This section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the present invention. The following discussion is intended to provide information to facilitate a better understanding of the present invention. Accordingly, it should be understood that statements in the following discussion are to be read in this light, and not as admissions of prior art.
Ubiquity of machine-to-machine (M2M) applications prevents maintaining many wireless devices in the always connected state due to the great number of connection resources needed, and the resulting denial of such resources to other devices to do otherwise.
Applications of these devices need short round-trip delay (RTD), e.g., approximately 100 ms or less; such applications include, but are not limited to, traffic control, gaming, location tracking, real-time machinery control, etc.
Setting up the full wireless connection will take longer than the required response time as they do not need long connected time or transfer a large amount of data, but connect quickly and may connect frequently.
In fact, most such applications complete within a single 3-way handshake of datagrams and the connection resource should immediately be freed. The device can send a connection close message to the wireless network, immediately after it has sent its acknowledgement of receiving the response from the remote server. Alternatively, the network can also send a connection close message to the wireless device, after a few seconds of inactivity between the device and the network (as it is currently done normally).
Actual wireless connections (depicted in FIG. 1) are a specialized technical term and a limited resource within a wireless network. An almost unlimited number of devices can be in the Idle State, i.e., listening to the network activities and network broadcast system information infrequently, but otherwise take no action. A larger number of devices may be in the Dormant State that occupies some resources such as shared or dedicated periodic transmission resources. Note, the Dormant State may also be variously named as Hold State, Suspended State, Cell_FACH State, etc. in different wireless technology, but they are commonly characterized by the fact that the wireless device and the wireless network already allocates the over-the-air and terrestrial network resources, but typically not a dedicated physical wireless connection. There can be a finite and relatively small number of devices in the connected State, where the device possesses full over-the-air and terrestrial network resources. In this state, the device can transmit data immediately to the network and vice versa.
This invention reduces the round-trip delay (RTD) of datagram exchanges between the wireless device and the remote server to approximately one hundred milliseconds or less.
If the device is initially in the Idle State, the reduction may be a few hundred milliseconds. If in the Hold State, the reduction is smaller, and may be tens of milliseconds to 100 milliseconds. The device sends the datagram over the (common) access channel (ACH) piggy-backed on the initial connection setup request. As the connection setup procedure requires, the device and the wireless network are already in a state to listen to the transmission of the wireless network throughout the connection setup process. The wireless network transmits the server response immediately over the (common) control channel (CCH), again piggy-backed on the traffic channel assignment (TCA) message, and thus avoiding any wait-time for the completion of the connection setup for the initial datagram exchange.
Examples of Supported Applications: Traffic Light Control
In certain jurisdictions, public transport vehicles are assigned privileges such that, for example, when a bus approaches a junction, an on-site traffic control device senses the approaching bus. The device sends a message to the remote traffic control server under the management of the said jurisdiction to signal that a bus is near the junction. Part of the privileges affords that the bus should proceed without stopping. The remote traffic control server is programmed such that it responds with an instruction, as encapsulated in a datagram, to turn the light in the direction of the bus Green and similarly lights in other directions Red. The bus does not stop or only needs to slow briefly, and can cross the junction with privilege ahead of other traffic. From the time the on-site traffic control device sends the message to the time that the instruction in response is received, the round trip delay (RTD) is required to be within tens of milliseconds, and with reliability of 95%.
There are four existing solutions for delivering machine-to-machine datagram exchanges:
Waiting for Connection Setup Completion: The wireless device initiates a connection setup with the wireless network, and waits for the connection to be fully set up to deliver the response from the remote server. This is shown in FIG. 2. (Note, in this method, we assume that the device can send the initial datagram over the ACH as uplink Data-over-Signaling, which is the more optimistic case by this method, and more efficient than waiting until the connection setup to deliver the datagram.)
The connection setup can take an additional 100 to 500 milliseconds, depending on the wireless technology, before the response can be delivered to the wireless device.
Base Station (BTS) Quick Connect: A variant of the first method is as illustrated in FIG. 3; once the device sends a connection request (which may or may not be together with uplink Data-over-Signaling), the connection is setup immediately at the BTS without involving a radio network controller (RNC), and thus eliminating the delays incurred over the backhaul network between the BTS and the central offices where the RNC is located. This has the benefit of expediting connection setup, but actual data exchange still has to wait until the completion of the connection setup.
Downlink Data-over-Signaling: The datagram exchange between the wireless device and the remote server can all be accomplished by sending the initial datagram from the device as a uplink Data-over-Signaling (DoS) message, which is encapsulated in a signaling message over common wireless channels, and the response from the server over downlink DoS on the common control channel (CCH), and without needing the setup of a connection between the device and the wireless network.
This solution is suboptimal as the downlink DoS message fails to exploit the reciprocity of the datagram exchange, and may involve sending the downlink DoS to the whole paging area of the device. Additionally sending these datagrams over the downlink DoS is a potential waste of common signaling resources as a large number of these, and over a large paging area, may be needed.
Wireless Technology Optimization: The wireless technology may be optimized in several ways to improve connection setup speed, and the wait-time for the initial datagram to begin transmission. For example, the device may be held in a more advanced state than Dormant State, e.g., a shared-dedicated state, whereby it can immediately send the datagram over the allocated resources with minimal contention or loss of reliability. Another example is to enhance the time-division multiplexing timing characteristics of the system such that each exchange in the connection setup process is faster.
This solution is possible for new wireless technologies, e.g., 3GPP Long-Term Evolution (LTE), but it is limited in existing wireless technologies, e.g., CDMA HRPD (or HRPD) and 3GPP UMTS, because such solutions typically entail significant system redesigns and additional changes have to be incorporated into the fundamental physical layer characteristics of the system.